A semiconductor device on a compound semiconductor substrate such as of gallium arsenide shows a high performance such as excellent high speed and light emitting property, which are not obtainable on silicon. However, the compound semiconductor substrate is associated with drawbacks of expensiveness, a low mechanical strength, difficulty in preparing a large-sized substrate etc.
Because of these facts, it has been tried to heteroepitaxially growing a compound semiconductor on a silicon substrate which can be obtained inexpensively, with a high mechanical strength and in a large-sized substrate. For example, Japanese Patents Nos. 3157030, 3237889 and 3237890 disclose a method of heteroepitaxially growing a compound semiconductor layer on a porous silicon layer formed on a silicon substrate, then bonding the silicon substrate with another substrate, and eliminating portions of the silicon substrate and of the porous silicon layer with an etching liquid to obtain a compound semiconductor substrate of a large area. Also Japanese Patent No. 2877800 discloses a method of growing a compound semiconductor layer on a porous silicon layer formed on a silicon substrate, then bonding the silicon substrate with another substrate, and breaking the porous silicon layer and dividing the bonded substrate by a fluid jet flow to obtain a compound semiconductor substrate.
As an example of a semiconductor device formed for example with gallium arsenide, a configuration of a light emitting diode chip is shown in FIG. 24. The configuration shown in FIG. 24 is basically constituted by laminating, on an n-GaAs substrate 51, an n-AlxGa1-xAs carrier confinement layer 53, an n-AlyGa1-yAs light emitting layer 54, and an n-AlxGa1-xAs carrier confinement layer 55. There are also provided a p-diffusion area 56 formed by locally diffusing Zn, an insulation layer 58, a metal electrode 59 formed in the p-diffusion area, and an n-side metal electrode 60 formed on the rear side of the GaAs substrate 51. In response to a current supply between the electrodes 59 and 60, a light emission is induced in the vicinity of a p-n junction interface close to a Zn diffusion front, but, as the light emission is omnidirectional, a part only of the light directed toward an exit window provided on the upper surface of the light emitting diode is emitted to the exterior.
In the configuration shown in FIG. 24, since the GaAs substrate 51 is absorbent to the emitted light, about 85% of the generated light is absorbed by the GaAs substrate 51. Also as the p-side metal electrode 59 formed on the p-diffusion area 56 constitutes a shield when the light generated in the light emitting layer is emitted to the exterior, the amount of light radiation is further decreased.
For example Japanese Patent Application Laid-open No. 11-168236 discloses a configuration of a light emitting diode capable of avoiding light absorption by a substrate, by adhering a semiconductor laminated portion constituted of a compound semiconductor to an alternative substrate different from a substrate used for crystal growth, then eliminating the substrate from the semiconductor laminated portion and providing a light reflecting layer such as a metal film between the semiconductor laminated portion and the alternative substrate.
In the producing method disclosed for example in Japanese Patent No. 3157030, a heteroepitaxial layer is formed by inserting a porous silicon layer is made present between the silicon and the compound semiconductor, thereby relaxing an mismatching of the lattice constants of silicon and compound semiconductor to a certain extent. However the crystallinity of the obtained compound semiconductor may still be insufficient, because it is not easy to eliminate the mismatching in the lattice constants of the porous silicon and the compound semiconductor. Also, depending on the specification of the desired compound semiconductor device, the compound semiconductor substrate obtained by such producing method is limited in its applicable range, and may not be able to fully exploit the advantage of the compound semiconductor device.
Also in the producing method for the light emitting diode disclosed in Japanese Patent Application Laid-open No. 11-168236, a substrate of a thickness of 300 to 500 μm is eliminated by grinding or the like from the semiconductor laminated portion of a thickness of several micrometers. In such elimination by grinding, it is difficult to uniformly control the film thickness of the semiconductor laminated portion, and it may become impossible to fully exploit the advantage of the compound semiconductor device.